1. Field of the Invention
The present invention relates to a spacer device for accurately locating and positioning wire reinforcement in molds for concrete structures, such as pipe, walls, slabs and the like. More particularly, it relates to a reinforcement spacer device which is of a high strength construction for heavy load applications.
2. The Prior Art
In the manufacture of reinforced concrete structures, such as concrete pipe, walls, slabs and the like, it is important that the steel reinforcement, typically in the form of welded-wire mesh, be properly positioned in the cross section of the designed structure. Improper positioning of the reinforcement degrades the structural integrity of the unit and, in a severe case, can lead to structural failure. Moreover, as labor skill and costs are significant factors in the manufacture of reinforced concrete structures, it is also important that the positioning of the reinforcement be carried out in as simple and straightforward, yet accurate, a manner as possible. A number of efforts have been made in the past to develop techniques and equipment that facilitate the correct placement of the steel reinforcement. Such efforts, however, have not fully addressed the problems involved nor provided solutions for those problems.
In the past, spacers provided have been composed of a light gauge metal band having opposite hook ends which were intended to engage parallel wires of the mesh. These spacers are sufficiently resilient to grip the wire mesh, yet light enough to allow "snap-on" application by hand. One such spacer is disclosed in the applicant's own U.S. Pat. No. 3,471,986, issued on Oct. 14, 1969.
The light-weight construction of the prior spacer, however, limits its use in heavy-duty applications, as it is susceptible of being dislodged or distorted in heavy-duty applications. In the case of concrete pipe, the device also is sometimes subject to side loads due to rotation of the mold around the reinforcing mesh, as the wall of the mold occasionally catches the edges of the spacer.
Another prior art spacer, described in U.S. Pat. No. 4,301,638, issued on Nov. 24, 1981, is a wire formed generally in a U-shape, providing parallel radial projections and duplicate pairs of hooks for clamping parallel wires of the mesh. The U-portion itself provides a looped lever arm for receiving a tool for forcibly applying the spacer to the wire mesh. While the device is stronger than those previously known, its hairpin-like structure permits the separate wire arms to deform relative to each other under side loading during radial compacting of the moist concrete, thus weakening the final product. Further, the hairpin structure with its loop tends to trap larger pieces of aggregate during concrete pouring, thereby inhibiting the free flow of concrete and creating voids, which weaken the structure of the final product.
Due to its U-shaped parallel wire structure, the '638 patent device is overly bulky, resulting in increased packing and shipping costs. As a matter of great practical inconvenience in the field, the hairpin-like structure results in the spacers becoming thoroughly entangled with each other during packing and shipment, which requires considerable time and labor to individually untangle the U-shaped spacers before they can be applied to the mesh wires. Still further, the duplicate hook and bight structure is complex and requires nearly exact parallelism, resulting in increased cost of manufacture.